1 Chronicles 23:3, 24-27

He counted the Levites who were thirty years old and older. In all, there were thirty-eight thousand Levites.

These were Levi’s descendants listed by their families. They were the leaders of families. Each person who was twenty years old or older was listed. They served in the LORD’s Temple. David had said, “The LORD, the God of Israel, has given rest to his people. He has come to live in Jerusalem forever. So the Levites don’t need to carry the Holy Tent or any of the things used in its services anymore.” David’s last instructions were to count the Levites who were twenty years old and older.